How Menstrual Cycle Underway

Did you know that when a baby girl is born, she has far more eggs in her body than she will ever use, of 450,000? They are stored in the ovaries, each inside its own sac called a follicle. When he was growing up, at puberty, his body begins producing various hormones that cause the eggs to mature. This was the beginning of the first cycle (called menarkhe), a cycle that will be repeated throughout life until menopause.

Typical menstrual cycle, from the first day of bleeding following the first day of bleeding, is divided into three parts: the follicular phase, ovulatory phase, and the luteal phase.

Follicular phase
The first part is from day 1 to ovulation. This is called the follicular phase, because the most important thing at this stage is the maturation of follicles. In a 28-day cycle, the phase is about 14 days shorter in shorter cycles, longer in the long cycle.

Let's start with the hypothalamus. The hypothalamus is a gland in the brain which is responsible for regulating thirst, hunger, sleep patterns, libido and endocrine function. It releases chemical messengers called follicle stimulating hormone releasing factor (FSH-RF) which tells the pituitary, another gland in the brain, in order to do its job. Pituitary later issued a follicle stimulating hormone (FSH) and a bit of luteinizing hormone (LH) into the bloodstream which causes the follicles begin to mature (number of follicles ranging from 3-30).

Mature follicles then release another hormone, estrogen. Estrogen is produced by cells surrounding the egg in the ovarian follicle (called granulosa cells). As the follicles mature for about seven days, more estrogen is released into the bloodstream. The main function of estrogen is to thicken the uterine wall. This causes the cervical mucus changes. When the estrogen level reaches a certain point, the hypothalamus releases luteinizing hormone releasing factor (LH-RF), which ordered the pituitary gland to release large amounts of luteinizing hormone (LH). This LH surge triggers the most mature follicle to rupture and release the egg. This is called ovulation. (Birth control pills usually work by blocking this LH surge, thus inhibiting the release of an egg.)
 
Ovulatory phase
This is the shortest phase, which occurs about 16-32 after the LH surge.

Just before ovulation, increases blood supply to the ovary and ovarian ligament to close the contract with the fallopian tubes, allowing the egg, once released, to find its way into the fallopian tubes. Just before ovulation, the cervix of women spend a lot of cervical mucus or stretchy like egg white pith. This mucus helps facilitate the movement of sperm toward the egg. Some women use daily mucous monitoring to determine when they are most likely to get pregnant. In the middle of this cycle, some women also experience cramping or other sensations. Basal body temperature increases after ovulation and stays higher by 0.5 degrees until a few days before the next period.

In the fallopian tube, the egg driven by small cells such as hair tipped-called "cilia", to the uterus. Fertilization occurs when no sperm are present.

Luteal Phase
The final phase is the luteal phase or post-ovulatory phase. Called the luteal phase because of the essential role played by the phase of the corpus luteum.

Around the time of ovulation, granulosa cells make estrogen change. The follicle from which the egg is released turns into the corpus luteum (yellow body), which produces progesterone (progestin). The most important role of progesterone is causing changes in the endometrium so that the uterus to receive the embryo implantation. Without progesterone, pregnancy can not occur. (Some of the abortion drug works by blocking progesterone and stopping implantation).

In the next phase, if fertilization and implantation does not occur, the follicle turns white and is called the corpus albikan. Arteries in the endometrial lining to close, stopping the flow of blood to the surface layer. Blood will gather at "venous lakes" which, once full, burst and together form the endometrial lining of menstrual flow. Most periods last 4 to 8 days.